Indeed, the latest command line tools (clang version 7.3) don't compile polymake, neither the released version nor the latest development version. clang 7.0 (the previous version of the clt) are fine.

I currently cannot offer a solution, but I am working on it. I'll post again once this is fixed.

I'll also update the installation instructions in the next days and add information on how to install the perl readline module. You can also look at this Makefile that installs polymake and all necessary dependencies into a local folder (but does not check whether anything is already present). It also installs the perl module.

Remember to add the path to the module to $PERL5LIB so that polymake can find it.